If you expand combobox next to the search textbox and scroll page then position of the combobox is changing too.
Maybe it isn't most important for working page properly, but during scrolling page up you can't have combobox expanded (it will cover up some part of page). It will be fixed to screen position not to page content.
Before scroll
After scroll page down
I am using Google Chrome v62.0.3209.94 (64-bit) on Windows 10.
